Infection causes serious complications during the healing process of acute and chronic wounds. Formation of biofilm contributes to the chronicity of early infections [Rulík et al., 2011] which leads to the chronic inflammation of the wound scum thus preventing the wound healing and promoting the dissemination of the infection [Bjarnsholt, 2013].
Biofilms are agglomerates of microorganisms adhered to a wound scum or to the surfaces of the artificial implants such as joint implants, osteosynthesis materials, cement fixations or catheters inserted into the body of patient. Biofilm is also formed in connection with dental plaque, urinary tract infections, eye infections and infections of ear canal or middle ear. It is estimated that biofilm-related infections account for at least 80% of all human infections. Microorganisms living in biofilms are embedded in a matrix of extracellular polymer substances made of polysaccharides, alginates and other compounds [Bjarnsholt et al., 2013]. This matrix acts as protection against the effect of antibiotics, antiseptics and immunity system of organism. In the stage of mature biofilm, when the nutrients are depleted, the matrix of biofilm begins to fall apart under control in clusters, microorganisms detach and spread to new infection sites thus causing serious complications.
Treatment of topical infections, including chronic wounds and infections caused by biofilms adhering to artificial materials, is very difficult and the subsequences are alarming. Protection of our immunity against microorganisms in biofilms is not sufficient and impropriate applications of topical antibiotics or antiseptics may result to the occurrence of resistant strains of microorganisms which prevail over those sensitive. For an effective local therapy of infection caused by microbes in a biofilm, it is advisable to use combination of mechanical debridement with broad-spectrum antimicrobial agent and other compounds that penetrate inside the biofilm to kill bacteria or inhibit formation of biofilm. One of these possibilities is the application of commercially available wound dressings based on the local action of silver ions (Aquacel Ag+Extra). Action of powdered polymeric materials such Altrazeal is based on the providing ideal wound moisture which supports optimal cell function and regeneration of afflicted tissue.
One of the ways of increasing the therapeutic potential of local therapy of infected wound or preventing the infection adherence on the surface of artificial material is the application of antimicrobial peptides (AMP) [Zasloff, 2002]. It is well known that AMPs kill bacteria with mechanism of action which is markedly different from that of conventional antibiotics and does not develop bacterial resistance. Therefore AMPs are considered a promising supplement to, or substitute for, conventional antibiotics [Hancock and Sahl, 2006; Toke, 2005; Giuliani et al., 2007, Zaiou, 2007; Oyston et al., 2009; Baltzer and Brown, 2011; Yeung et al., 2011; Čeřovský, 2014].
Recently discovered and newly presented very effective AMPs represent convenient, synthetically available group of compounds aimed for the eradication of the infection or for the prevention of the emergence of the focus of infection. They can be applied in the combination with commercially available materials used as wound dressings, or as mixtures with carriers used in orthopedics for treatment of osteomyelitis, or as mixtures with synthetic polymeric materials used in orthopedics as the cements (polymethylmethacrylate) for endoprostheses fixation.
Antimicrobial peptides have been identified almost everywhere across the spectrum of animal and plant kingdoms. In the class of insects, AMPs represent a remarkable group which represent the main means of defense against microorganisms [Čeřovský, 2014; Otvos, 2000]. They kill bacteria and other microorganisms such as fungi with mechanism of action which is markedly different from that of conventional antibiotics and is assumed not to develop bacterial resistance. Although the precise mechanism of the broad spectrum of antimicrobial activity of these peptides is not yet fully understood, they appear to act via a specific, but not receptor-mediated, formation of trans-membrane pores or ion channels in cellular membrane. This causes leakage of essential metabolites that results in the disruption of microbial cell structure and leads to cell death [Oren and Shai, 1998; Yeaman and Yount, 2003; Nguyen at al., 2011]. Quite peculiar groups of peptides with antimicrobial properties were identified in the venom of stinging insects such as hymenopterans [Kuhn-Nentwig, 2003].
Antimicrobial effect of peptides isolated from the venoms of wasps, bees, bumblebees and ants is mostly secondary in the nature. Their main function consists of the toxicity, causing pain and inflammation, as it is in the case of peptides belonging to the group of mastoparans [Čeřovskýet al. 2008]. Nevertheless, antimicrobial effect of peptides isolated for example from the venom of wild bees is quite significant. With regard to their synthetic availability, these peptides may find application in practical medicine. The growing resistance of bacterial pathogens and yeasts to conventional antibiotics or commonly used antifungals has become serious global health problem which requires a persistent search for novel alternatives to traditional antibiotics. In such alarming situation, AMPs appear to be very promising compounds for developing drugs to fight resistant pathogens.
Natural peptide called hylanine was originally isolated from the venom reservoirs of solitary wild bees Hylaeus signatus, and its sequence was determined as follows:
(SEQ ID NO. 1)H-Gly-Ile-Met-Ser-Ser-Leu-Met-Lys-Lys-Leu-Ala-Ala-His-Ile-Ala-Lys-NH2
Based on this sequence, hylanine was prepared by the method of solid phase peptide synthesis followed by testing of its antimicrobial activity.
Synthetically prepared hylanine exhibited high antimicrobial activity against Micrococcus luteus and Bacillus subtilis and moderate activity against the yeast Candida albicans. However, its activity against all strains of pathogenic Staphylococcus aureus and Pseudomonas aeruginosa was weak. Nevertheless, its toxicity against eukaryotic cells measured as hemolytic activity was very low.
Even though the primary role of hylanine in the nature is not known, we deal with novel unique peptide with significant biological properties. However, it is generally known, that the peptides isolated from the venom of the insect of the Hymenoptera order exhibit antimicrobial and antifungal effect, eventually kill the cells of protozoal parasites or some cancer cells.